1 @c Copyright (C) 2002 Free Software Foundation, Inc.
2 @c This is part of the GnuPG manual.
3 @c For copying conditions, see the file gnupg.texi.
5 @c Note that we use this texinfo file for all versions of GnuPG:
6 @c 2.0 and 2.1. The macro "gpgtwoone" controls parts which are only
7 @c valid for GnuPG 2.1 and later.
10 @node Invoking GPG-AGENT
11 @chapter Invoking GPG-AGENT
12 @cindex GPG-AGENT command options
13 @cindex command options
14 @cindex options, GPG-AGENT command
19 \- Secret key management for GnuPG
50 @command{gpg-agent} is a daemon to manage secret (private) keys
51 independently from any protocol. It is used as a backend for
52 @command{gpg} and @command{gpgsm} as well as for a couple of other
56 The agent is automatically started on demand by @command{gpg},
57 @command{gpgsm}, @command{gpgconf}, or @command{gpg-connect-agent}.
58 Thus there is no reason to start it manually. In case you want to use
59 the included Secure Shell Agent you may start the agent using:
62 gpg-connect-agent /bye
68 The usual way to run the agent is from the @code{~/.xsession} file:
71 eval $(gpg-agent --daemon)
74 If you don't use an X server, you can also put this into your regular
75 startup file @code{~/.profile} or @code{.bash_profile}. It is best not
76 to run multiple instance of the @command{gpg-agent}, so you should make
77 sure that only one is running: @command{gpg-agent} uses an environment
78 variable to inform clients about the communication parameters. You can
79 write the content of this environment variable to a file so that you can
80 test for a running agent. Here is an example using Bourne shell syntax:
83 gpg-agent --daemon --enable-ssh-support \
84 --write-env-file "$@{HOME@}/.gpg-agent-info"
87 This code should only be run once per user session to initially fire up
88 the agent. In the example the optional support for the included Secure
89 Shell agent is enabled and the information about the agent is written to
90 a file in the HOME directory. Note that by running gpg-agent without
91 arguments you may test whether an agent is already running; however such
92 a test may lead to a race condition, thus it is not suggested.
95 The second script needs to be run for each interactive session:
98 if [ -f "$@{HOME@}/.gpg-agent-info" ]; then
99 . "$@{HOME@}/.gpg-agent-info"
100 export GPG_AGENT_INFO
106 It reads the data out of the file and exports the variables. If you
107 don't use Secure Shell, you don't need the last two export statements.
111 You should always add the following lines to your @code{.bashrc} or
112 whatever initialization file is used for all shell invocations:
120 It is important that this environment variable always reflects the
121 output of the @code{tty} command. For W32 systems this option is not
124 Please make sure that a proper pinentry program has been installed
125 under the default filename (which is system dependant) or use the
126 option @option{pinentry-program} to specify the full name of that program.
127 It is often useful to install a symbolic link from the actual used
128 pinentry (e.g. @file{/usr/bin/pinentry-gtk}) to the expected
129 one (e.g. @file{/usr/bin/pinentry}).
133 @xref{Option Index},for an index to @command{GPG-AGENT}'s commands and options.
137 * Agent Commands:: List of all commands.
138 * Agent Options:: List of all options.
139 * Agent Configuration:: Configuration files.
140 * Agent Signals:: Use of some signals.
141 * Agent Examples:: Some usage examples.
142 * Agent Protocol:: The protocol the agent uses.
149 Commands are not distinguished from options except for the fact that
150 only one command is allowed.
155 Print the program version and licensing information. Note that you cannot
156 abbreviate this command.
161 Print a usage message summarizing the most useful command-line options.
162 Note that you cannot abbreviate this command.
165 @opindex dump-options
166 Print a list of all available options and commands. Note that you cannot
167 abbreviate this command.
171 Run in server mode and wait for commands on the @code{stdin}. The
172 default mode is to create a socket and listen for commands there.
174 @item --daemon [@var{command line}]
176 Start the gpg-agent as a daemon; that is, detach it from the console
177 and run it in the background.
179 Because @command{gpg-agent} prints out
180 important information required for further use, a common way of
181 invoking gpg-agent is: @code{eval $(gpg-agent --daemon)} to setup the
182 environment variables. The option @option{--write-env-file} is
183 another way commonly used to do this.
185 Yet another way is creating
186 a new process as a child of gpg-agent: @code{gpg-agent --daemon
187 /bin/sh}. This way you get a new shell with the environment setup
188 properly; if you exit from this shell, gpg-agent terminates as well.
193 @section Option Summary
197 @anchor{option --options}
198 @item --options @var{file}
200 Reads configuration from @var{file} instead of from the default
201 per-user configuration file. The default configuration file is named
202 @file{gpg-agent.conf} and expected in the @file{.gnupg} directory directly
203 below the home directory of the user.
205 @anchor{option --homedir}
206 @include opt-homedir.texi
212 Outputs additional information while running.
213 You can increase the verbosity by giving several
214 verbose commands to @command{gpgsm}, such as @samp{-vv}.
219 Try to be as quiet as possible.
223 Don't invoke a pinentry or do any other thing requiring human interaction.
225 @item --faked-system-time @var{epoch}
226 @opindex faked-system-time
227 This option is only useful for testing; it sets the system time back or
228 forth to @var{epoch} which is the number of seconds elapsed since the year
231 @item --debug-level @var{level}
233 Select the debug level for investigating problems. @var{level} may be
234 a numeric value or a keyword:
238 No debugging at all. A value of less than 1 may be used instead of
241 Some basic debug messages. A value between 1 and 2 may be used
242 instead of the keyword.
244 More verbose debug messages. A value between 3 and 5 may be used
245 instead of the keyword.
247 Even more detailed messages. A value between 6 and 8 may be used
248 instead of the keyword.
250 All of the debug messages you can get. A value greater than 8 may be
251 used instead of the keyword. The creation of hash tracing files is
252 only enabled if the keyword is used.
255 How these messages are mapped to the actual debugging flags is not
256 specified and may change with newer releases of this program. They are
257 however carefully selected to best aid in debugging.
259 @item --debug @var{flags}
261 This option is only useful for debugging and the behaviour may change at
262 any time without notice. FLAGS are bit encoded and may be given in
263 usual C-Syntax. The currently defined bits are:
267 X.509 or OpenPGP protocol related data
269 values of big number integers
271 low level crypto operations
277 show memory statistics.
279 write hashed data to files named @code{dbgmd-000*}
281 trace Assuan protocol
283 bypass all certificate validation
288 Same as @code{--debug=0xffffffff}
290 @item --debug-wait @var{n}
292 When running in server mode, wait @var{n} seconds before entering the
293 actual processing loop and print the pid. This gives time to attach a
296 @item --debug-quick-random
297 @opindex debug-quick-random
298 This option inhibits the use the very secure random quality level
299 (Libgcrypt’s @code{GCRY_VERY_STRONG_RANDOM}) and degrades all request
300 down to standard random quality. It is only used for testing and
301 shall not be used for any production quality keys. This option is
302 only effective when given on the command line.
306 Don't detach the process from the console. This is mainly useful for
315 Format the info output in daemon mode for use with the standard Bourne
316 shell or the C-shell respectively. The default is to guess it based on
317 the environment variable @code{SHELL} which is correct in almost all
321 @item --write-env-file @var{file}
322 @opindex write-env-file
323 Often it is required to connect to the agent from a process not being an
324 inferior of @command{gpg-agent} and thus the environment variable with
325 the socket name is not available. To help setting up those variables in
326 other sessions, this option may be used to write the information into
327 @var{file}. If @var{file} is not specified the default name
328 @file{$@{HOME@}/.gpg-agent-info} will be used. The format is suitable
329 to be evaluated by a Bourne shell like in this simple example:
332 eval $(cat @var{file})
333 eval $(cut -d= -f 1 < @var{file} | xargs echo export)
340 Tell the pinentry not to grab the keyboard and mouse. This option
341 should in general not be used to avoid X-sniffing attacks.
343 @anchor{option --log-file}
344 @item --log-file @var{file}
346 Append all logging output to @var{file}. This is very helpful in seeing
347 what the agent actually does. If neither a log file nor a log file
348 descriptor has been set on a Windows platform, the Registry entry
349 @code{HKCU\Software\GNU\GnuPG:DefaultLogFile}, if set, is used to specify
353 @anchor{option --allow-mark-trusted}
354 @item --allow-mark-trusted
355 @opindex allow-mark-trusted
356 Allow clients to mark keys as trusted, i.e. put them into the
357 @file{trustlist.txt} file. This is by default not allowed to make it
358 harder for users to inadvertently accept Root-CA keys.
360 @anchor{option --allow-preset-passphrase}
361 @item --allow-preset-passphrase
362 @opindex allow-preset-passphrase
363 This option allows the use of @command{gpg-preset-passphrase} to seed the
364 internal cache of @command{gpg-agent} with passphrases.
367 @anchor{option --allow-loopback-pinentry}
368 @item --allow-loopback-pinentry
369 @opindex allow-loopback-pinentry
370 Allow clients to use the loopback pinentry features; see the option
371 @option{pinentry-mode} for details.
374 @item --ignore-cache-for-signing
375 @opindex ignore-cache-for-signing
376 This option will let @command{gpg-agent} bypass the passphrase cache for all
377 signing operation. Note that there is also a per-session option to
378 control this behaviour but this command line option takes precedence.
380 @item --default-cache-ttl @var{n}
381 @opindex default-cache-ttl
382 Set the time a cache entry is valid to @var{n} seconds. The default is
385 @item --default-cache-ttl-ssh @var{n}
386 @opindex default-cache-ttl
387 Set the time a cache entry used for SSH keys is valid to @var{n}
388 seconds. The default is 1800 seconds.
390 @item --max-cache-ttl @var{n}
391 @opindex max-cache-ttl
392 Set the maximum time a cache entry is valid to @var{n} seconds. After
393 this time a cache entry will be expired even if it has been accessed
394 recently or has been set using @command{gpg-preset-passphrase}. The
395 default is 2 hours (7200 seconds).
397 @item --max-cache-ttl-ssh @var{n}
398 @opindex max-cache-ttl-ssh
399 Set the maximum time a cache entry used for SSH keys is valid to
400 @var{n} seconds. After this time a cache entry will be expired even
401 if it has been accessed recently or has been set using
402 @command{gpg-preset-passphrase}. The default is 2 hours (7200
405 @item --enforce-passphrase-constraints
406 @opindex enforce-passphrase-constraints
407 Enforce the passphrase constraints by not allowing the user to bypass
408 them using the ``Take it anyway'' button.
410 @item --min-passphrase-len @var{n}
411 @opindex min-passphrase-len
412 Set the minimal length of a passphrase. When entering a new passphrase
413 shorter than this value a warning will be displayed. Defaults to 8.
415 @item --min-passphrase-nonalpha @var{n}
416 @opindex min-passphrase-nonalpha
417 Set the minimal number of digits or special characters required in a
418 passphrase. When entering a new passphrase with less than this number
419 of digits or special characters a warning will be displayed. Defaults
422 @item --check-passphrase-pattern @var{file}
423 @opindex check-passphrase-pattern
424 Check the passphrase against the pattern given in @var{file}. When
425 entering a new passphrase matching one of these pattern a warning will
426 be displayed. @var{file} should be an absolute filename. The default is
427 not to use any pattern file.
429 Security note: It is known that checking a passphrase against a list of
430 pattern or even against a complete dictionary is not very effective to
431 enforce good passphrases. Users will soon figure up ways to bypass such
432 a policy. A better policy is to educate users on good security
433 behavior and optionally to run a passphrase cracker regularly on all
434 users passphrases to catch the very simple ones.
436 @item --max-passphrase-days @var{n}
437 @opindex max-passphrase-days
438 Ask the user to change the passphrase if @var{n} days have passed since
439 the last change. With @option{--enforce-passphrase-constraints} set the
440 user may not bypass this check.
442 @item --enable-passphrase-history
443 @opindex enable-passphrase-history
444 This option does nothing yet.
446 @item --pinentry-program @var{filename}
447 @opindex pinentry-program
448 Use program @var{filename} as the PIN entry. The default is installation
451 @item --pinentry-touch-file @var{filename}
452 @opindex pinentry-touch-file
453 By default the filename of the socket gpg-agent is listening for
454 requests is passed to Pinentry, so that it can touch that file before
455 exiting (it does this only in curses mode). This option changes the
456 file passed to Pinentry to @var{filename}. The special name
457 @code{/dev/null} may be used to completely disable this feature. Note
458 that Pinentry will not create that file, it will only change the
459 modification and access time.
462 @item --scdaemon-program @var{filename}
463 @opindex scdaemon-program
464 Use program @var{filename} as the Smartcard daemon. The default is
465 installation dependent and can be shown with the @command{gpgconf}
468 @item --disable-scdaemon
469 @opindex disable-scdaemon
470 Do not make use of the scdaemon tool. This option has the effect of
471 disabling the ability to do smartcard operations. Note, that enabling
472 this option at runtime does not kill an already forked scdaemon.
475 @item --disable-check-own-socket
476 @opindex disable-check-own-socket
477 @command{gpg-agent} employs a periodic self-test to detect a stolen
478 socket. This usually means a second instance of @command{gpg-agent}
479 has taken over the socket and @command{gpg-agent} will then terminate
480 itself. This option may be used to disable this self-test for
484 @item --use-standard-socket
485 @itemx --no-use-standard-socket
486 @opindex use-standard-socket
487 @opindex no-use-standard-socket
489 Since GnuPG 2.1 the standard socket is always used. These options
493 By enabling this option @command{gpg-agent} will listen on the socket
494 named @file{S.gpg-agent}, located in the home directory, and not create
495 a random socket below a temporary directory. Tools connecting to
496 @command{gpg-agent} should first try to connect to the socket given in
497 environment variable @var{GPG_AGENT_INFO} and then fall back to this
498 socket. This option may not be used if the home directory is mounted on
499 a remote file system which does not support special files like fifos or
502 Note, that @option{--use-standard-socket} is the default on
505 The default may be changed at build time. It is
506 possible to test at runtime whether the agent has been configured for
507 use with the standard socket by issuing the command @command{gpg-agent
508 --use-standard-socket-p} which returns success if the standard socket
509 option has been enabled.
512 @item --display @var{string}
513 @itemx --ttyname @var{string}
514 @itemx --ttytype @var{string}
515 @itemx --lc-ctype @var{string}
516 @itemx --lc-messages @var{string}
517 @itemx --xauthority @var{string}
524 These options are used with the server mode to pass localization
528 @itemx --keep-display
530 @opindex keep-display
531 Ignore requests to change the current @code{tty} or X window system's
532 @code{DISPLAY} variable respectively. This is useful to lock the
533 pinentry to pop up at the @code{tty} or display you started the agent.
535 @anchor{option --enable-ssh-support}
536 @item --enable-ssh-support
537 @opindex enable-ssh-support
539 Enable the OpenSSH Agent protocol.
541 In this mode of operation, the agent does not only implement the
542 gpg-agent protocol, but also the agent protocol used by OpenSSH
543 (through a separate socket). Consequently, it should be possible to use
544 the gpg-agent as a drop-in replacement for the well known ssh-agent.
546 SSH Keys, which are to be used through the agent, need to be added to
547 the gpg-agent initially through the ssh-add utility. When a key is
548 added, ssh-add will ask for the password of the provided key file and
549 send the unprotected key material to the agent; this causes the
550 gpg-agent to ask for a passphrase, which is to be used for encrypting
551 the newly received key and storing it in a gpg-agent specific
554 Once a key has been added to the gpg-agent this way, the gpg-agent
555 will be ready to use the key.
557 Note: in case the gpg-agent receives a signature request, the user might
558 need to be prompted for a passphrase, which is necessary for decrypting
559 the stored key. Since the ssh-agent protocol does not contain a
560 mechanism for telling the agent on which display/terminal it is running,
561 gpg-agent's ssh-support will use the TTY or X display where gpg-agent
562 has been started. To switch this display to the current one, the
563 following command may be used:
566 gpg-connect-agent updatestartuptty /bye
569 Although all GnuPG components try to start the gpg-agent as needed, this
570 is not possible for the ssh support because ssh does not know about it.
571 Thus if no GnuPG tool which accesses the agent has been run, there is no
572 guarantee that ssh is abale to use gpg-agent for authentication. To fix
573 this you may start gpg-agent if needed using this simple command:
576 gpg-connect-agent /bye
579 Adding the @option{--verbose} shows the progress of starting the agent.
583 All the long options may also be given in the configuration file after
584 stripping off the two leading dashes.
588 @node Agent Configuration
589 @section Configuration
591 There are a few configuration files needed for the operation of the
592 agent. By default they may all be found in the current home directory
593 (@pxref{option --homedir}).
598 @cindex gpg-agent.conf
599 This is the standard configuration file read by @command{gpg-agent} on
600 startup. It may contain any valid long option; the leading
601 two dashes may not be entered and the option may not be abbreviated.
602 This file is also read after a @code{SIGHUP} however only a few
603 options will actually have an effect. This default name may be
604 changed on the command line (@pxref{option --options}).
605 You should backup this file.
608 This is the list of trusted keys. You should backup this file.
610 Comment lines, indicated by a leading hash mark, as well as empty
611 lines are ignored. To mark a key as trusted you need to enter its
612 fingerprint followed by a space and a capital letter @code{S}. Colons
613 may optionally be used to separate the bytes of a fingerprint; this
614 allows to cut and paste the fingerprint from a key listing output. If
615 the line is prefixed with a @code{!} the key is explicitly marked as
618 Here is an example where two keys are marked as ultimately trusted
619 and one as not trusted:
623 # CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
624 A6935DD34EF3087973C706FC311AA2CCF733765B S
626 # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
627 DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S
629 # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
630 !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
634 Before entering a key into this file, you need to ensure its
635 authenticity. How to do this depends on your organisation; your
636 administrator might have already entered those keys which are deemed
637 trustworthy enough into this file. Places where to look for the
638 fingerprint of a root certificate are letters received from the CA or
639 the website of the CA (after making 100% sure that this is indeed the
640 website of that CA). You may want to consider allowing interactive
641 updates of this file by using the @xref{option --allow-mark-trusted}.
642 This is however not as secure as maintaining this file manually. It is
643 even advisable to change the permissions to read-only so that this file
644 can't be changed inadvertently.
646 As a special feature a line @code{include-default} will include a global
647 list of trusted certificates (e.g. @file{/etc/gnupg/trustlist.txt}).
648 This global list is also used if the local list is not available.
650 It is possible to add further flags after the @code{S} for use by the
657 Relax checking of some root certificate requirements. As of now this
658 flag allows the use of root certificates with a missing basicConstraints
659 attribute (despite that it is a MUST for CA certificates) and disables
660 CRL checking for the root certificate.
663 If validation of a certificate finally issued by a CA with this flag set
664 fails, try again using the chain validation model.
671 This file is used when support for the secure shell agent protocol has
672 been enabled (@pxref{option --enable-ssh-support}). Only keys present in
673 this file are used in the SSH protocol. You should backup this file.
675 The @command{ssh-add} tool may be used to add new entries to this file;
676 you may also add them manually. Comment lines, indicated by a leading
677 hash mark, as well as empty lines are ignored. An entry starts with
678 optional whitespace, followed by the keygrip of the key given as 40 hex
679 digits, optionally followed by the caching TTL in seconds and another
680 optional field for arbitrary flags. A non-zero TTL overrides the global
681 default as set by @option{--default-cache-ttl-ssh}.
683 The only flag support is @code{confirm}. If this flag is found for a
684 key, each use of the key will pop up a pinentry to confirm the use of
685 that key. The flag is automatically set if a new key was loaded into
686 @code{gpg-agent} using the option @option{-c} of the @code{ssh-add}
689 The keygrip may be prefixed with a @code{!} to disable an entry entry.
691 The following example lists exactly one key. Note that keys available
692 through a OpenPGP smartcard in the active smartcard reader are
693 implicitly added to this list; i.e. there is no need to list them.
697 # Key added on: 2011-07-20 20:38:46
698 # Fingerprint: 5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81
699 34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm
703 @item private-keys-v1.d/
705 This is the directory where gpg-agent stores the private keys. Each
706 key is stored in a file with the name made up of the keygrip and the
707 suffix @file{key}. You should backup all files in this directory
708 and take great care to keep this backup closed away.
713 Note that on larger installations, it is useful to put predefined
714 files into the directory @file{/etc/skel/.gnupg/} so that newly created
715 users start up with a working configuration. For existing users the
716 a small helper script is provided to create these files (@pxref{addgnupghome}).
725 @section Use of some signals.
726 A running @command{gpg-agent} may be controlled by signals, i.e. using
727 the @command{kill} command to send a signal to the process.
729 Here is a list of supported signals:
735 This signal flushes all cached passphrases and if the program has been
736 started with a configuration file, the configuration file is read
737 again. Only certain options are honored: @code{quiet},
738 @code{verbose}, @code{debug}, @code{debug-all}, @code{debug-level},
739 @code{no-grab}, @code{pinentry-program}, @code{default-cache-ttl},
740 @code{max-cache-ttl}, @code{ignore-cache-for-signing},
741 @code{allow-mark-trusted}, @code{disable-scdaemon}, and
742 @code{disable-check-own-socket}. @code{scdaemon-program} is also
743 supported but due to the current implementation, which calls the
744 scdaemon only once, it is not of much use unless you manually kill the
750 Shuts down the process but waits until all current requests are
751 fulfilled. If the process has received 3 of these signals and requests
752 are still pending, a shutdown is forced.
756 Shuts down the process immediately.
760 Dump internal information to the log file.
764 This signal is used for internal purposes.
776 It is important to set the GPG_TTY environment variable in
777 your login shell, for example in the @file{~/.bashrc} init script:
781 export GPG_TTY=$(tty)
785 If you enabled the Ssh Agent Support, you also need to tell ssh about
786 it by adding this to your init script:
791 if [ "$@{gnupg_SSH_AUTH_SOCK_by:-0@}" -ne $$ ]; then
792 export SSH_AUTH_SOCK="$@{HOME@}/.gnupg/S.gpg-agent.ssh"
799 The usual way to invoke @command{gpg-agent} is
802 $ eval $(gpg-agent --daemon)
805 An alternative way is by replacing @command{ssh-agent} with
806 @command{gpg-agent}. If for example @command{ssh-agent} is started as
807 part of the Xsession initialization, you may simply replace
808 @command{ssh-agent} by a script like:
814 exec /usr/local/bin/gpg-agent --enable-ssh-support --daemon \
815 --write-env-file $@{HOME@}/.gpg-agent-info "$@@"
820 and add something like (for Bourne shells)
824 if [ -f "$@{HOME@}/.gpg-agent-info" ]; then
825 . "$@{HOME@}/.gpg-agent-info"
826 export GPG_AGENT_INFO
833 to your shell initialization file (e.g. @file{~/.bashrc}).
841 @section Agent's Assuan Protocol
843 Note: this section does only document the protocol, which is used by
844 GnuPG components; it does not deal with the ssh-agent protocol.
847 The @command{gpg-agent} daemon is started on demand by the GnuPG
851 The @command{gpg-agent} should be started by the login shell and set an
852 environment variable to tell clients about the socket to be used.
853 Clients should deny to access an agent with a socket name which does
854 not match its own configuration. An application may choose to start
855 an instance of the gpg-agent if it does not figure that any has been
856 started; it should not do this if a gpg-agent is running but not
857 usable. Because @command{gpg-agent} can only be used in background mode, no
858 special command line option is required to activate the use of the
862 To identify a key we use a thing called keygrip which is the SHA-1 hash
863 of an canonical encoded S-Expression of the public key as used in
864 Libgcrypt. For the purpose of this interface the keygrip is given as a
865 hex string. The advantage of using this and not the hash of a
866 certificate is that it will be possible to use the same keypair for
867 different protocols, thereby saving space on the token used to keep the
871 The @command{gpg-agent} may send status messages during a command or when
872 returning from a command to inform a client about the progress or result of an
873 operation. For example, the @var{INQUIRE_MAXLEN} status message may be sent
874 during a server inquire to inform the client of the maximum usable length of
875 the inquired data (which should not be exceeded).
879 * Agent PKDECRYPT:: Decrypting a session key
880 * Agent PKSIGN:: Signing a Hash
881 * Agent GENKEY:: Generating a Key
882 * Agent IMPORT:: Importing a Secret Key
883 * Agent EXPORT:: Exporting a Secret Key
884 * Agent ISTRUSTED:: Importing a Root Certificate
885 * Agent GET_PASSPHRASE:: Ask for a passphrase
886 * Agent CLEAR_PASSPHRASE:: Expire a cached passphrase
888 * Agent PRESET_PASSPHRASE:: Set a passphrase for a keygrip
890 * Agent GET_CONFIRMATION:: Ask for confirmation
891 * Agent HAVEKEY:: Check whether a key is available
892 * Agent LEARN:: Register a smartcard
893 * Agent PASSWD:: Change a Passphrase
894 * Agent UPDATESTARTUPTTY:: Change the Standard Display
895 * Agent GETEVENTCOUNTER:: Get the Event Counters
896 * Agent GETINFO:: Return information about the process
897 * Agent OPTION:: Set options for the session
900 @node Agent PKDECRYPT
901 @subsection Decrypting a session key
903 The client asks the server to decrypt a session key. The encrypted
904 session key should have all information needed to select the
905 appropriate secret key or to delegate it to a smartcard.
911 Tell the server about the key to be used for decryption. If this is
912 not used, @command{gpg-agent} may try to figure out the key by trying to
913 decrypt the message with each key available.
919 The agent checks whether this command is allowed and then does an
920 INQUIRY to get the ciphertext the client should then send the cipher
924 S: INQUIRE CIPHERTEXT
930 Please note that the server may send status info lines while reading the
931 data lines from the client. The data send is a SPKI like S-Exp with
937 (<param_name1> <mpi>)
939 (<param_namen> <mpi>)))
942 Where algo is a string with the name of the algorithm; see the libgcrypt
943 documentation for a list of valid algorithms. The number and names of
944 the parameters depend on the algorithm. The agent does return an error
945 if there is an inconsistency.
947 If the decryption was successful the decrypted data is returned by
950 Here is an example session:
954 S: INQUIRE CIPHERTEXT
955 C: D (enc-val elg (a 349324324)
956 C: D (b 3F444677CA)))
958 S: # session key follows
960 S: D (value 1234567890ABCDEF0)
961 S: OK descryption successful
965 The “PADDING” status line is only send if gpg-agent can tell what kind
966 of padding is used. As of now only the value 0 is used to indicate
967 that the padding has been removed.
971 @subsection Signing a Hash
973 The client ask the agent to sign a given hash value. A default key
974 will be chosen if no key has been set. To set a key a client first
981 This can be used multiple times to create multiple signature, the list
982 of keys is reset with the next PKSIGN command or a RESET. The server
983 test whether the key is a valid key to sign something and responds with
987 SETHASH --hash=<name>|<algo> <hexstring>
990 The client can use this command to tell the server about the data <hexstring>
991 (which usually is a hash) to be signed. <algo> is the decimal encoded hash
992 algorithm number as used by Libgcrypt. Either <algo> or --hash=<name>
993 must be given. Valid names for <name> are:
997 The SHA-1 hash algorithm
999 The SHA-256 hash algorithm
1001 The RIPE-MD160 hash algorithm
1003 The old and broken MD5 hash algorithm
1005 A combined hash algorithm as used by the TLS protocol.
1009 The actual signing is done using
1015 Options are not yet defined, but my later be used to choose among
1016 different algorithms. The agent does then some checks, asks for the
1017 passphrase and as a result the server returns the signature as an SPKI
1018 like S-expression in "D" lines:
1023 (<param_name1> <mpi>)
1025 (<param_namen> <mpi>)))
1029 The operation is affected by the option
1032 OPTION use-cache-for-signing=0|1
1035 The default of @code{1} uses the cache. Setting this option to @code{0}
1036 will lead @command{gpg-agent} to ignore the passphrase cache. Note, that there is
1037 also a global command line option for @command{gpg-agent} to globally disable the
1041 Here is an example session:
1049 S: # I did ask the user whether he really wants to sign
1050 S: # I did ask the user for the passphrase
1052 C: D ABCDEF012345678901234
1054 S: # signature follows
1055 S: D (sig-val rsa (s 45435453654612121212))
1061 @subsection Generating a Key
1063 This is used to create a new keypair and store the secret key inside the
1064 active PSE --- which is in most cases a Soft-PSE. An not yet defined
1065 option allows to choose the storage location. To get the secret key out
1066 of the PSE, a special export tool has to be used.
1070 GENKEY [--no-protection] [--preset] [<cache_nonce>]
1077 Invokes the key generation process and the server will then inquire
1078 on the generation parameters, like:
1082 C: D (genkey (rsa (nbits 1024)))
1086 The format of the key parameters which depends on the algorithm is of
1092 (parameter_name_1 ....)
1094 (parameter_name_n ....)))
1097 If everything succeeds, the server returns the *public key* in a SPKI
1098 like S-Expression like this:
1107 Here is an example session:
1112 C: D (genkey (rsa (nbits 1024)))
1115 S: D (rsa (n 326487324683264) (e 10001)))
1121 The @option{--no-protection} option may be used to prevent prompting for a
1122 passphrase to protect the secret key while leaving the secret key unprotected.
1123 The @option{--preset} option may be used to add the passphrase to the cache
1124 using the default cache parameters.
1128 @subsection Importing a Secret Key
1130 This operation is not yet supported by GpgAgent. Specialized tools
1131 are to be used for this.
1133 There is no actual need because we can expect that secret keys
1134 created by a 3rd party are stored on a smartcard. If we have
1135 generated the key ourself, we do not need to import it.
1138 @subsection Export a Secret Key
1142 Should be done by an extra tool.
1144 @node Agent ISTRUSTED
1145 @subsection Importing a Root Certificate
1147 Actually we do not import a Root Cert but provide a way to validate
1148 any piece of data by storing its Hash along with a description and
1149 an identifier in the PSE. Here is the interface description:
1152 ISTRUSTED <fingerprint>
1155 Check whether the OpenPGP primary key or the X.509 certificate with the
1156 given fingerprint is an ultimately trusted key or a trusted Root CA
1157 certificate. The fingerprint should be given as a hexstring (without
1158 any blanks or colons or whatever in between) and may be left padded with
1159 00 in case of an MD5 fingerprint. GPGAgent will answer with:
1165 The key is in the table of trusted keys.
1168 ERR 304 (Not Trusted)
1171 The key is not in this table.
1173 Gpg needs the entire list of trusted keys to maintain the web of
1174 trust; the following command is therefore quite helpful:
1180 GpgAgent returns a list of trusted keys line by line:
1183 S: D 000000001234454556565656677878AF2F1ECCFF P
1184 S: D 340387563485634856435645634856438576457A P
1185 S: D FEDC6532453745367FD83474357495743757435D S
1189 The first item on a line is the hexified fingerprint where MD5
1190 fingerprints are @code{00} padded to the left and the second item is a
1191 flag to indicate the type of key (so that gpg is able to only take care
1192 of PGP keys). P = OpenPGP, S = S/MIME. A client should ignore the rest
1193 of the line, so that we can extend the format in the future.
1195 Finally a client should be able to mark a key as trusted:
1198 MARKTRUSTED @var{fingerprint} "P"|"S"
1201 The server will then pop up a window to ask the user whether she
1202 really trusts this key. For this it will probably ask for a text to
1203 be displayed like this:
1206 S: INQUIRE TRUSTDESC
1207 C: D Do you trust the key with the fingerprint @@FPR@@
1208 C: D bla fasel blurb.
1213 Known sequences with the pattern @@foo@@ are replaced according to this
1218 Format the fingerprint according to gpg rules for a v3 keys.
1220 Format the fingerprint according to gpg rules for a v4 keys.
1222 Choose an appropriate format to format the fingerprint.
1224 Replaced by a single @code{@@}
1227 @node Agent GET_PASSPHRASE
1228 @subsection Ask for a passphrase
1230 This function is usually used to ask for a passphrase to be used for
1231 conventional encryption, but may also be used by programs which need
1232 special handling of passphrases. This command uses a syntax which helps
1233 clients to use the agent with minimum effort.
1236 GET_PASSPHRASE [--data] [--check] [--no-ask] [--repeat[=N]] \
1237 [--qualitybar] @var{cache_id} \
1238 [@var{error_message} @var{prompt} @var{description}]
1241 @var{cache_id} is expected to be a string used to identify a cached
1242 passphrase. Use a @code{X} to bypass the cache. With no other
1243 arguments the agent returns a cached passphrase or an error. By
1244 convention either the hexified fingerprint of the key shall be used for
1245 @var{cache_id} or an arbitrary string prefixed with the name of the
1246 calling application and a colon: Like @code{gpg:somestring}.
1248 @var{error_message} is either a single @code{X} for no error message or
1249 a string to be shown as an error message like (e.g. "invalid
1250 passphrase"). Blanks must be percent escaped or replaced by @code{+}'.
1252 @var{prompt} is either a single @code{X} for a default prompt or the
1253 text to be shown as the prompt. Blanks must be percent escaped or
1254 replaced by @code{+}.
1256 @var{description} is a text shown above the entry field. Blanks must be
1257 percent escaped or replaced by @code{+}.
1259 The agent either returns with an error or with a OK followed by the hex
1260 encoded passphrase. Note that the length of the strings is implicitly
1261 limited by the maximum length of a command. If the option
1262 @option{--data} is used, the passphrase is not returned on the OK line
1263 but by regular data lines; this is the preferred method.
1265 If the option @option{--check} is used, the standard passphrase
1266 constraints checks are applied. A check is not done if the passphrase
1267 has been found in the cache.
1269 If the option @option{--no-ask} is used and the passphrase is not in the
1270 cache the user will not be asked to enter a passphrase but the error
1271 code @code{GPG_ERR_NO_DATA} is returned.
1273 If the option @option{--qualitybar} is used and a minimum passphrase
1274 length has been configured, a visual indication of the entered
1275 passphrase quality is shown.
1278 CLEAR_PASSPHRASE @var{cache_id}
1281 may be used to invalidate the cache entry for a passphrase. The
1282 function returns with OK even when there is no cached passphrase.
1286 @node Agent CLEAR_PASSPHRASE
1287 @subsection Remove a cached passphrase
1289 Use this command to remove a cached passphrase.
1293 CLEAR_PASSPHRASE [--mode=normal] <cache_id>
1296 CLEAR_PASSPHRASE <cache_id>
1301 The @option{--mode=normal} option can be used to clear a @var{cache_id} that
1302 was set by gpg-agent.
1308 @node Agent PRESET_PASSPHRASE
1309 @subsection Set a passphrase for a keygrip
1311 This command adds a passphrase to the cache for the specified @var{keygrip}.
1314 PRESET_PASSPHRASE [--inquire] <string_or_keygrip> <timeout> [<hexstring>]
1317 The passphrase is a hexidecimal string when specified. When not specified, the
1318 passphrase will be retrieved from the pinentry module unless the
1319 @option{--inquire} option was specified in which case the passphrase will be
1320 retrieved from the client.
1322 The @var{timeout} parameter keeps the passphrase cached for the specified
1323 number of seconds. A value of @code{-1} means infinate while @code{0} means
1324 the default (currently only a timeout of -1 is allowed, which means to never
1331 @node Agent GET_CONFIRMATION
1332 @subsection Ask for confirmation
1334 This command may be used to ask for a simple confirmation by
1335 presenting a text and 2 buttons: Okay and Cancel.
1338 GET_CONFIRMATION @var{description}
1341 @var{description}is displayed along with a Okay and Cancel
1342 button. Blanks must be percent escaped or replaced by @code{+}. A
1343 @code{X} may be used to display confirmation dialog with a default
1346 The agent either returns with an error or with a OK. Note, that the
1347 length of @var{description} is implicitly limited by the maximum
1348 length of a command.
1353 @subsection Check whether a key is available
1355 This can be used to see whether a secret key is available. It does
1356 not return any information on whether the key is somehow protected.
1359 HAVEKEY @var{keygrips}
1362 The agent answers either with OK or @code{No_Secret_Key} (208). The
1363 caller may want to check for other error codes as well. More than one
1364 keygrip may be given. In this case the command returns success if at
1365 least one of the keygrips corresponds to an available secret key.
1369 @subsection Register a smartcard
1375 This command is used to register a smartcard. With the --send
1376 option given the certificates are send back.
1380 @subsection Change a Passphrase
1384 PASSWD [--cache-nonce=<c>] [--passwd-nonce=<s>] [--preset] @var{keygrip}
1387 PASSWD @var{keygrip}
1391 This command is used to interactively change the passphrase of the key
1392 identified by the hex string @var{keygrip}.
1395 The @option{--preset} option may be used to add the new passphrase to the
1396 cache using the default cache parameters.
1400 @node Agent UPDATESTARTUPTTY
1401 @subsection Change the standard display
1407 Set the startup TTY and X-DISPLAY variables to the values of this
1408 session. This command is useful to direct future pinentry invocations
1409 to another screen. It is only required because there is no way in the
1410 ssh-agent protocol to convey this information.
1413 @node Agent GETEVENTCOUNTER
1414 @subsection Get the Event Counters
1420 This function return one status line with the current values of the
1421 event counters. The event counters are useful to avoid polling by
1422 delaying a poll until something has changed. The values are decimal
1423 numbers in the range @code{0} to @code{UINT_MAX} and wrapping around to
1424 0. The actual values should not be relied upon; they shall only be used
1427 The currently defined counters are are:
1430 Incremented with any change of any of the other counters.
1432 Incremented for added or removed private keys.
1434 Incremented for changes of the card readers stati.
1438 @subsection Return information about the process
1440 This is a multipurpose function to return a variety of information.
1446 The value of @var{what} specifies the kind of information returned:
1449 Return the version of the program.
1451 Return the process id of the process.
1453 Return the name of the socket used to connect the agent.
1454 @item ssh_socket_name
1455 Return the name of the socket used for SSH connections. If SSH support
1456 has not been enabled the error @code{GPG_ERR_NO_DATA} will be returned.
1460 @subsection Set options for the session
1462 Here is a list of session options which are not yet described with
1463 other commands. The general syntax for an Assuan option is:
1466 OPTION @var{key}=@var{value}
1470 Supported @var{key}s are:
1473 @item agent-awareness
1474 This may be used to tell gpg-agent of which gpg-agent version the
1475 client is aware of. gpg-agent uses this information to enable
1476 features which might break older clients.
1479 Change the session's environment to be used for the
1480 Pinentry. Valid values are:
1484 Delete envvar @var{name}
1486 Set envvar @var{name} to the empty string
1487 @item @var{name}=@var{value}
1488 Set envvar @var{name} to the string @var{value}.
1491 @item use-cache-for-signing
1492 See Assuan command @code{PKSIGN}.
1494 @item allow-pinentry-notify
1495 This does not need any value. It is used to enable the
1496 PINENTRY_LAUNCHED inquiry.
1500 This option is used to change the operation mode of the pinentry. The
1501 following values are defined:
1505 This is the default mode which pops up a pinentry as needed.
1508 Instead of popping up a pinentry, return the error code
1509 @code{GPG_ERR_CANCELED}.
1512 Instead of popping up a pinentry, return the error code
1513 @code{GPG_ERR_NO_PIN_ENTRY}.
1516 Use a loopback pinentry. This fakes a pinentry by using inquiries
1517 back to the caller to ask for a passphrase. This option may only be
1518 set if the agent has been configured for that.
1519 Use the @xref{option --allow-loopback-pinentry}.
1525 @item cache-ttl-opt-preset
1526 This option sets the cache TTL for new entries created by GENKEY and
1527 PASSWD commands when using the @option{--preset} option. It it is not
1528 used a default value is used.
1533 Instead of using the standard S2K count (which is computed on the
1534 fly), the given S2K count is used for new keys or when changing the
1535 passphrase of a key. Values below 65536 are considered to be 0. This
1536 option is valid for the entire session or until reset to 0. This
1537 option is useful if the key is later used on boxes which are either
1538 much slower or faster than the actual box.
1548 @command{gpg-connect-agent}(1),
1549 @command{scdaemon}(1)
1551 @include see-also-note.texi